Kemi Badenoch is due to deliver her big speech to the Conservative Party conference on Wednesday. She will highlight key policies such as keeping the state pension triple lock and scrapping bizarre rules that currently take free childcare away from high earners. Itโ€™s rumoured there may even be some good news about cutting or ending inheritance tax, although nothing will be confirmed until the speech itself.

But her speech has taken on an added urgency after Labour Prime Minister Andy Burnhamโ€™s unashamed left-wing speech to his own conference last week. Because itโ€™s become clear the next general election may be Mrs Badenochโ€™s one and only chance to save her party – and save Britain. One of the most consequential announcements in Mr Burnhamโ€™s speech was his plan to change the UKโ€™s voting system.

It doesnโ€™t make headlines in the same way as his announcement that he wants to scrap the triple lock, or change our relationship with the EU – which, it was later confirmed, could mean scrapping Brexit entirely and re-joining.

Electoral reform and proportional representation donโ€™t sound very exciting.

But itโ€™s hugely important. Introducing proportional representation could lock the Conservatives out of power more or less forever.

It could mean Labour and the Liberal Democrats are in a permanent coalition, giving the UK a left-wing government in perpetuity.

Lib Dem voters come in all shapes and sizes. Many of them have no love for Labour. There are parts of the country where people who are natural Conservatives switch to the Lib Dems when the Tory Party has upset them. They certainly arenโ€™t socialists.

But Lib Dem activists and MPs are a different matter. They are left-wingers.

Proportional representation would almost certainly mean that no party in Parliament has a majority. In order to form a government, parties would need to work together.

Unless voting habits across the UK change significantly, it would mean the Lib Dems hold the balance of power. They would decide who runs the country, by deciding which party to join forces with.

Itโ€™s true that in 2010, the Lib Dems did a deal with the Tories. But they now regard this as a terrible mistake. And that was when the Conservatives were led by a self-proclaimed liberal, David Cameron. The Tories have moved to the right since then, and are likely to stay there.

So in the future, proportional representation is expected to give us a Labour-Lib Dem alliance – time after time.

And it could get even worse. Fringe parties like the Greens could also become part of the left-wing coalition.

Mr Burnham faces one obstacle. Many of his own MPs hate the idea of proportional representation, because they donโ€™t want to be in a coalition witn the Lib Dems. They prefer the current voting system, which at least gives Labour a chance of winning an overall majority in Parliament.

But if he gets his way, Labour will change the voting system if it wins the next general election.

So Mrs Badenoch and her Tory team needs to stop that happening – or risk being exiled from power for the foreseeable future.